1. Field of the Invention
The present invention relates to hybrid laminates and to manufacturing methods therefor, and more particularly, relates to a hybrid laminate which is provided with a functional material layer comprising a ceramic material having a specific electric property, such as dielectricity, magnetism, resistivity and insulation, and which can be advantageously used for electronic devices, such as multilayer circuit boards and electronic devices in the form of chips, and to a manufacturing method therefor.
2. Description of the Related Art
As laminates of interest in the present invention, there is, for example, a unit body in the form of a chip having a laminated structure provided in a multilayer circuit board having a laminated structure or an electronic device. The internal structures of these multilayer circuit boards and unit bodies, in general, are provided with internal conductive members, such as, internal electrodes or via hole connecting portions.
When substrates used for the multilayer circuit boards and unit bodies, as described above, are composed of a ceramic, a baking step for the substrate for sintering the ceramic is generally required in the production thereof. Consequently, the internal conductive members are also treated by baking during the baking step for the substrate.
In order to meet current requirements for higher frequency and higher speed of signals in the field of electronic apparatuses, low resistance metals, such as silver, gold and copper, must be used as conductive components for the internal conductive members described above.
Under the circumstances thus described, in order to make the internal conductive members provided with conductive components of low resistance metals, such as silver, gold and copper, simultaneously sinterable when the substrate is sintered, the substrate must be sinterable at, for example, 1,000.degree. C. or less. Consequently, as an ingredient material for the substrate, a composite material including glass in addition to the ceramic, in which the glass functions as an auxiliary agent for sintering a ceramic, is advantageously used.
By using glass-ceramic multilayer circuit boards provided with the substrate composed of a composite of a glass and a ceramic, as described above, high-density-wiring and a thin-layer structure can be realized, whereby, in response to recent trends to make electronic chip devices compact and light-weight, demands to make circuit boards to be mounted with these chip devices compact and light-weight can also be advantageously satisfied.
As an embodiment of glass-ceramic multilayer circuit boards, there is a glass-ceramic multilayer circuit board obtained by simultaneously baking a substrate and a functional material, in which, on a green sheet containing glass powders and ceramic powders to be formed into a substrate, functional material is formed by coating functional material slurry containing powders composed of a ceramic having specific electric properties, such as dielectricity and magnetism, or by laminating a green sheet formed by molding. According to the glass-ceramic multilayer circuit boards described above, a specific function or multiple functions can be given thereto.
When the glass-ceramic multilayer circuit boards described above are produced, the functional material is simultaneously baked with the substrate. Consequently, an appropriate amount of the glass powders, which are the same as those contained in the substrate, is added to the functional material slurry to minimize differences in coefficients of expansion between the substrate and the functional material slurry during baking and differences in shrinkage rates therebetween during sintering so as to prevent occurrence of defects, such as separations at the interface.
In addition, after a mother laminate is formed by employing a manufacturing method substantially equivalent to that used for producing the glass-ceramic multilayer circuit board using the functional material slurry described above, chips used as unit bodies for a plurality of electronic devices can be obtained by cutting the mother laminate.
FIG. 1 is a capacitor 1, produced by the method described above, shown in a cross-sectional view.
The capacitor 1 is provided with a unit body 5 composed of a laminate having a functional material layer 2 and substrates 3 and 4 disposed so as to be in contact with both sides of the functional material layer 2. Internal electrodes 6 and 7 as internal conductive members are formed along the individual interfaces of the functional material layer 2 with substrates 3 and 4 so as to oppose each other with the functional material layer 2 therebetween. The internal electrodes 6 and 7 extend to opposing edge faces 8 and 9 of the unit body 5, and are connected to external electrodes 10 and 11 formed on the edge faces 8 and 9, respectively.
The unit body 5 described above is obtained by cutting a mother laminate, and the mother laminate is provided with elements individually corresponding to the functional material layer 2, the substrate layers 3 and 4, and the internal electrodes 6 and 7.
The substrate layers 3 and 4, at a stage before baking is performed, contain glass powders and ceramic powders. In addition, the functional material layer 2, at a stage before baking is performed, contains powders composed of a dielectric ceramic having a dielectric property. The mother laminate or the unit body 5 is obtained after the baking step. In order to minimize differences in coefficients of expansion between the substrates 3 and 4 and the functional material layer 2 during baking and differences in shrinkage rates therebetween during sintering, an appropriate amount of the glass powders, which are the same as those contained in the substrates 3 and 4, is added to the functional material slurry to be formed into the functional material layer 2.
As has been thus described, the functional material layer 2 in the capacitor 1 contains the dielectric ceramic so as to yield greater static capacitance between the internal electrodes 6 and 7. Accordingly, the dielectric ceramic contained in the functional material layer 2 preferably has a higher density.
However, in order to decrease differences in coefficients of expansion between the substrates 3 and 4 and the functional material layer 2 during baking and differences in shrinkage rates therebetween during sintering, a certain amount of the glass powders, which are the same as those contained in the substrates 3 and 4, is necessarily added to the functional material layer 2. As a result, the density of the dielectric ceramic contained in the functional material layer 2 may be decreased, and a dielectric property required for the functional material layer 2 may be degraded in some cases.